Utilizing ICR equilibrium constant determinations, intrinsic (gas phase) hydrogen-bond acceptor strengths are being determined to establish the major effects of molecular structure. Relationships between intrinsic hydrogen-bond strengths, proton affinities, cation hydration energies and hydrogen-bond strengths in solution are under investigation. Biologically important hydrogen-bond acceptors and donors are given emphasis. Methods of linear free energy and structure-reactivity relationships are applied to analyze results. Both a physical picture of, and energetics for the hydration or solvation of, organic cations will be approached in terms of a model utilizing discrete equilibria for successive attachments of "individual" molecules. Utilizing F19 and C13 -NMR methods for equilibrium constant determinations, studies of hydrogen-bonding interactions in solution will be obtained to evaluate (by comparison with corresponding gas phase results) the role of the solvent. Effects of hydroxylic solvent self-association on proton-transfer processes will be investigated.